1. Field of the Invention
The present invention relates to a battery with a film casing and a method of manufacturing the same, and more particularly, to a sealed battery with a film casing having a reliable terminal structure.
2. Description of the Related Art
In recent years, to meet a demand of a battery having higher capacity and smaller size, a lithium ion battery has been used as a power source of mobile equipment such as a mobile phone and a digital still camera. In addition, the lithium ion battery which has a high energy density and does not have a memory effect is also used as a power source for an electric bicycle, an electric tool, or an electric car. Smaller size is required in the mobile equipment and power source, and in accordance therewith, the lithium ion battery has required to be designed smaller and thinner in shape.
A battery, in which a plurality of positive electrodes and negative electrodes having a flat-plate shape are stacked via a separator, a power collection tab connected to each of the electrodes is connected in parallel to one another, and the electrodes are covered by a flexible film casing such as a laminated film obtained by laminating a metal film such as an aluminum foil and a synthetic resin film, has been used. Such a film casing is characterized in that water and gas do not pass through, and that a sealing characteristic by heat welding is excellent.
FIG. 7 is a plan view explaining a conventional battery with a film casing.
A battery 1 with a film casing has a battery element 2 covered by a film casing 3 obtained by laminating an aluminum foil and a synthetic resin film. In addition, an electrode terminal 4A on a positive electrode side and an electrode terminal 4B on a negative electrode side bonded with the battery element 2 are sealed at a sealing part 5 of the film casing 3.
In addition, a periphery of a part positioned at the sealing part 5 of the electrode terminals 4A and 4B is covered by an insulating resin layer 6 extending beyond the sealing part 5, and the insulating resin layer 6 is sealed and integrated with the film casing 3 at the sealing part 5 by a method such as heat welding. As a result, there is no possibility that the metal layer such as an aluminum foil configuring the film casing and the electrode terminal contact with each other, and a short circuit due to the aluminum foil which is a component member of the film casing can be prevented.
In addition, JP-A-2000-21387 proposes the prevention of a short circuit of a positive electrode terminal and a negative electrode terminal by exposing an adhesive layer positioned at an inner surface side of the battery on the film casing more outwardly than a metallic foil.
When the positive and negative electrode terminals of the battery with a film casing is connected to a circuit substrate and a protective element, or when a plurality of batteries are connected in series or in parallel to manufacture a battery module, it is essential that the electrode terminals are bent in order to reduce the size of battery module.
However, when the electrode terminals are bent in the battery shown in FIG. 7, a part covered by the insulating resin layer 6 has strength against bending higher than other parts and the electrode terminals bend at an edge of the insulating resin layer 6. Therefore, it has been difficult to bend the part covered by the insulating resin layer. As a result, the electrode terminals are bent along a bending line 7.
However, when the electrode terminals 4A and 4B are bent at an edge of the insulating resin layer 6, there has been a possibility that the electrode terminals are cut due to lower strength against bending. Therefore, there has been a problem in terms of reliability.